Even more about money. My understanding was that NASA came up with a big, awesome plan for a reusable spacecraft kinda resembling the shuttle, and only doing stuff that NASA and their science/exploration missions needed, but they couldn't get anywhere near enough money to build it. So they went to the military to try and get some more money, and they said that they'd kick in some towards it if it could do these other missions they wanted too. They took it and ended up building something that didn't do anybody's mission really well, but it was the only way at the time to get enough money to get something off the ground.